Attic insulation help needed

[oberah]

Hi, I had a question regarding attic insulation. I moved into our new home a year ago, 2 story home, 2008 build, with an attic (attic is approx 1500 sq ft). When we moved in, the attic had probably 2-3 inches of sparsely covered loose insulation and out upstairs was noticeably colder despite central heating.
I had approx 9 inches of loose insulation blown in to cover the entire attic floor which made quite a bit of difference.
I would like to cover approx 50% of my attic with OSB sheets so that I can use it for some storage, and also put down some sheets of fiberglass insulation throughout as well since our winters are progressively getting colder her in missouri.
Is there any drawback of adding osb subfloor to part of the attic, with regard to weight on the ceiling joists? Is there a problem in compressing the current insulation down so that it is below the OSB with regard to insulation effectiveness or moisture retention?
Thank you

 

[dishdude]

I wouldn't worry about weight but compressing the insulation will slightly reduce it's effectiveness. You also don't want to compress the insulation to the point it's putting pressure on the drywall.

Honestly this all sounds like a giant hassle, maybe a garage sale would be a better alternative? Getting stuff in and out of the attic and storing in an area that isn't climate controlled isn't that great.

 

[Lubener]

The compressing of the insulation will compromise its effectiveness.. I wouldn't do it. As mentiones, you would also chance on damaging the ceiling drywall below. If you have trusses up in the attic, I would be careful with the weight and quantity of items you store up in your attic. Attic "floors" with trusses cannot take a lot of weight being up there.

 

[pcoxe]

Attics are not good storage spaces. Only store things that you will eventually throw away there. Many salvage places sell ready built backyard storage sheds. That would likely be your most affordable alternative to redesigning an attic.

 

[burbguy82]

1.) You need to make sure that you can place some sheets in the attic, making sure the weight can be carried, and that there are no wires routed on the top s of the joists that will get pinched. If the joists are 2x8, then it will likely be fine for some storage but not of 500 dead bodies, and shamoos carcass. Be careful with this.

If the joists are engineer, pressed plate connection style, and are 2x4 you can only place sheeting where there is a load bearing wall underneath, not just a wall, a load bearing wall.

2.) yes the insulation factor will be less

 

[JohnnyG]

I read a several years ago that SLIGHTLY compressing fiberglass insulation actually increases its effectiveness. Insulation traps air movement and hence heat transfer, as long as the air can still be trapped, it will insulate just fine, if not slightly better.
If you are really worried, install some polyisocyanate board (1/2" is about R4.5) (no foil needed) under the plywood first.

I just looked it up. Compressing fiberglass batt insulation (6" batt) by 50% reduces the R value from R19 to R14. so slight compression won't hurt. (Johns Manville website)

Be careful not to trap moisture in the enclosed area.

 

[RhondaHonda]

It’s probably 2x4 trusses so I wouldn’t add any weight other than insulation up there.

 

[Donald]

Make sure you have the l rafter vents so blown insulation does not block the venting from soffit to ridge.

 

[alarmguy]

I had approx 9 inches of loose insulation blown in to cover the entire attic floor which made quite a bit of difference ... Is there a problem in compressing the current insulation down so that it is below the OSB with regard to insulation effectiveness or moisture retention?
Thank you

You would be best off moving the insulation and not compressing it. If you are compressing it I would do not more than an inch or two.
Much more and you will bring down the insulation r factor to around the same as a 2x4 exterior wall of R15 or less.
(Using the example posted by @JohnnyG )